Grub 2 Basics

On that page are links to a variety of other Grub 2 pages which cover installation, troubleshooting, ISO booting, Grub menu displays, and more. The majority of those pages were migrated from threads started on the Ubuntu Forums.

Thank you to all the users who posted in these threads and expanded our knowledge of Grub 2 since it's introduction.

Support threads regarding the wiki and it's content should be created in a suitable forum.

The Grub 2 Guide
(formerly Grub 2 Basics)

Better Documentation - Get It From the Grub 2 Developers
This thread is more than two years old. It was written at a time when Grub 2 was very new and there was very little documentation for end users. Fortunately, over time, the documentation has been greatly improved and GUI apps have been developed to assist users. Two important sources of Grub 2 information are the GNU Grub Manual and on-line information available by running the following command:

Code:

info -f grub -n 'Simple configuration'

Grub 1.99 / Natty: Black Screen, with or without blinking cursor
If your boot in Natty ends up at a blank black screen, or a screen with a blinking cursor, take a look at the following thread. Forum member MAFoElffen has done some great research and has come up with some workarounds that may get your system booted. Here is the thread:Graphics Resolution- Upgrade /Blank Screen after reboot

Repair Using the Correct CD !
It appears that Grub 1.98 and Grub 1.99 don't get along well. If having to repair a Grub 2 problem using a LiveCD, make sure the OS and CD are for the same release (Natty LiveCD for Natty, Maverick LiveCD for Maverick, etc). This includes running the 'grub-install' command to write to the MBR.

While menuentries generated with Grub 1.99 work correctly, menuentries from older custom menus or imported from earlier Grub 2 menus may produce the above errors. The reason is a format change to the "set" section of the 'search' line.
Old:

New for Natty - Grub 1.99 (RC) - Drag & Drop GRUB Background
For Ubuntu 11.04 Natty and Grub 1.99RC: Place a graphic in /boot/grub, run update-grub and you should have a Grub menu background image. Read more in this thread:Grub 2 Drop-In Backgrounds & Fonts

GUI Apps for Grub 2 - Finally some apps for the GUI enthusiast!Grub Customizer - Daniel Richter has developed a graphical Grub2 configuration application. It's an excellent step in making Grub2 menu changes simpler for the average user. It provides users with a method of altering their Grub2 menus without using the command line and obscure commands. The application is available from this Launchpad page. How it works is detailed in this FAQ. Here is the Ubuntu Forum HOWTO on Grub Customizer:Grub Customizer

Boot Repair - Forum member YannBuntu has developed an app which helps repair the MBR or purge and restore Grub 2 without having to use the terminal extensively. If a terminal command is required, the app tells you what it is. Here is the forum link:[Boot-Repair] Graphical tool to repair the PC boot in 1 clic !

Thanks to Daniel and YannBuntu for providing these apps to the Ubuntu community.

GRUB Changes to /etc/default/grub Options
Grub 1.98 has made some changes, and Grub 1.99 is making more to the options available in /etc/default/grub. To see the current options available to /etc/default/grub for your version:

Code:

grep "export GRUB_DEVICE" -A42 /usr/sbin/grub-mkconfig

For instance, in Grub 1.98 and earlier, the /etc/default/grub entry to hide "Recovery" menu entries was "GRUB_DISABLE_LINUX_RECOVERY=true". In G2 1.99 it is currently "GRUB_DISABLE_RECOVERY=true".

Wubi Megathread Guide
Having problems with your Wubi installation? Forum member Rubi1200 has written an excellent comprehensive guide on resolving Wubi-related problems. View the "Wubi Megathread" at http://ubuntuforums.org/showthread.php?t=1639198

Grub Submenu
Test versions of Ubuntu 11.04 (Natty Narwhale) are being released with Grub 1.99. One of the new features is the use of the Submenu. The submenu is still being tweaked, but should hide older kernels in the main OS. Clicking on the Submenu entry will reveal the underlying older kernels. Using a Submenu kernel as the default initially was not possible, but a patch has been submitted by Colin Watson. The user will be able to use either the exact menuentry title or the "saved" function in /etc/default/grub's GRUB_DEFAULT= setting to set a submenu default. The use of a number in GRUB_DEFAULT is currently not possible. More details as they become available.

Introduction

First Look Differences

Improvements

Booting Grub

Grub 2 Files & Options

Adding Entries to Grub 2

Removing Entries from Grub 2

Grub 2 Splash Images & Theming

Changing Menu Resolution

Password Protection

Booting to Recovery Mode w/o Menu Option

Uninstalling GRUB 2 > GRUB

Reinstalling GRUB 2 from the LiveCD

Booting to LiveCD ISO

Booting from the Rescue Mode

Restoring GRUB2 / XP / Vista / Win 7 Bootloaders

Grub Rescue Image

Grub 2 Fallback Option

Selected Problems & Bugs

Links

Introduction
I've written this guide to present some basic information about Grub 2, now the default bootloader on all supported Ubuntu Desktops. There are now versions 1.97~beta, 1.98 (Lucid/Maverick) and 1.99 (Natty), with improvements (and file changes) in each subsequent version. Since Lucid is the LTS, references to Grub 2 will refer to 1.98 unless otherwise noted. The user can check their current version with the "grub-install -v" command.

Grub 2 GUI Apps: There are currently 3 GUI apps which support Grub 2. This guide primarily deals with the terminal and editing files, since the thread was originally created when there was little to no support for Grub 2. Startup Manager: Provides basic support for Grub 2 but not all options are available. The two most-used items, however, are: setting the default kernel/OS and setting the menu timeout delay. View the StartUpManager community doc or the forum post on which it was based: http://ubuntuforums.org/showthread.php?t=818177Grub Customizer: Designed by Daniel Richter for Grub 2 with a good variety of customization options. Here is a guide on installing and using GC:Grub CustomizerBoot Repair: A boot and Grub 2 repair app created by YannBuntu. Repair the MBR and purge/reinstall Grub 2 assistance.Boot-Repair

Official documentation for Grub 2 has been greatly expanded since it's release. The source document should take precedence over material found in this thread, unless otherwise noted. This link is to Grub 1.99:http://www.gnu.org/software/grub/manual/grub.html

For troubleshooting and modifying the Grub menu, it is important to know which version you are using (Grub legacy, 0.97; Grub 2 in Karmic 1.97~beta4; Grub 2 in Lucid 1.98, 1.99RC in Natty). To confirm the version of Grub used in your system, run this command:

First Look Differences: GRUB vs GRUB 2
At first boot, there will not be much difference in what the user sees on the boot menu. The one exception is a clean install of Ubuntu with no other installed operating system(s). In this case, GRUB 2 will boot directly to the login prompt or Desktop without displaying a menu. Other major differences:

No ''/boot/grub/menu.lst''. It has been replaced by ''/boot/grub/grub.cfg''.

Hold down SHIFT to display the hidden menu during boot (formerly ESC is GRUB legacy).

There is no "find /boot/grub/stage1" at the grub prompt. Stage 1.5 has also been eliminated.

The main menu file, ''/boot/grub/grub.cfg'' is not normally edited directly, as it will be overwritten by certain updates (see next).

''grub.cfg'' is overwritten when there is a Grub update, a kernel is added/removed or the user runs `update-grub` *

A pre-made custom file, ''/etc/grub.d/40_custom'', is available in which users can place their own entries. This file will not be overwritten by Grub updates.

* To update the GRUB 2 menu, the command sudo update-grub will be used throughout this guide. update-grub actually runs the command "grub-mkconfig -o /boot/grub/grub.cfg" This runs several scripts and incorporates the results into /boot/grub/grub.cfg which detemines what is seen on the screen during boot. Since the GRUB 2 developers do not intend to remove the update-grub 'stub', it will be used for simplicity and ease of use.

Improvements
GRUB 2's major improvements over the original GRUB include:

New configuration file structure

Scripting support including conditional statements and functions

Dynamic module loading

Rescue mode

Themes - under (very slow development). Users wishing to use theming should search the Internet for "burg".

Graphical boot menu support and improved splash capability

Boot Ubuntu LiveCD and some other ISO images directly from hard drive

Non-X86 platform support (such as PowerPC)

Universal support for UUIDs (not just Ubuntu)

Improved internationalization, including support for non-ASCII characters

Grub 2 will boot straight into the default operating system if no other operating system is detected. No menu will be displayed. If another operating system is detected, the Grub 2 menu will display.

Timed display.

The default delay is 10 seconds. If no user input is made Grub 2 boots to the default entry.

The countdown can be stopped by pressing any key. The user must then make a selection manually.

The booted entry is determined by the DEFAULT= setting in /etc/default/grub, The first "menuentry" is 0.

Hidden

The user can interrupt the boot process and display the menu by holding down the SHIFT key until the menu displays. Grub 2 searches for a depressed SHIFT key signal during boot. If the key is pressed or Grub 2 cannot determine the status of the key, the menu is displayed. Note: The "SHIFT" keystatus check is currently nested within in a conditional statement within /etc/grub.d/30_os-prober and may not work under certain circumstances.

The time the screen remains blank but available for display is determined by a setting in /etc/default/grub.

To provide visual feedback during while the countdown continues, a countdown display can be shown on the screen.

At the end of the timeout, the default entry determined in /etc/default/grub will be selected.

Saved

If the default option is set to "saved", the last kernel/system successfully booted will be selected and run if no input is made.

Unlike GRUB, GRUB 2 stores the "saved" entry as a string, not as a menu position number. In GRUB 2, the result is applied more consistently. Example: If the first entry (kernel -15) becomes the second entry due to a kernel update, it will still be the "saved" entry even though it's position on the menu has changed.

Grub 2 Files & Options
Many of the files in /boot/grub will not be recognizable by users of Grub Legacy. Especially noticeable are the multitude of *.mod files. Grub 2 is modular and these files are loaded as necessary by the grub bootloader.

The Grub 2 user-configurable settings are contained mainly in /etc/default/grub and the files in /etc/grub.d. When update-grub is executed the results are input into the /boot/grub/grub.cfg file.

/boot/grub/grub.cfg

This is the main Grub 2 file. It "replaces" Grub Legacy's /boot/grub/menu.lst This file contains the Grub menu information but unlike Grub Legacy's menu.lst file, grub.cfg is not normally meant to be edited as it is the product of Grub2 configuration scripts and is overwritten during certain updates. If a user edits grub.cfg, expect the changes to be removed during such updates or disable the ability of the OS to run these updates.

grub.cfg is automatcially generated when "update-grub" is executed:

Each section (### BEGIN) is clearly delineated and references the file in the /etc/grub.d folder from which the information was generated. The major default sections are 00_header, 05_debian_theme, 10_linux, 30_os-prober, and 40_custom.

grub.cfg is updated by running the "update-grub" or "update-grub2" command as root.

By default, and whenever the "update-grub" command is executed, this file is made "read-only". This is in keeping with the intent that the file should not be edited manually. If you must edit this file, instructions are provided in Section 2.

/etc/default/grub
Note: Online documentation regarding the options available in this file is available by running the following command in a terminal:

Code:

info -f grub -n 'Simple configuration'

This file contains information formerly contained in the upper section of Grub Legacy's menu.lst and items contained on the end of the kernel line. The items in this file can be edited by a user with administrator (root) privileges.

To find the options available in a specific version of Grub 2, open a terminal and run: grep "DEVICE" -A 40 /usr/sbin/grub-mkconfig

# If you change this file, run 'update-grub' afterwards to update
# /boot/grub/grub.cfg.

This setting allows the use of the following commands to set a default OS. The default OS will not be set merely by an interactive selection of an OS from the menu.

grub-set-default. Sets the default boot entry until changed.

The format is "sudo grub-set-default X, with X being the menuentry position (starting with 0 as the first entry) or the exact menu string. Examples: sudo grub-set-default 3 or sudo grub-set-default "Ubuntu, Linux 2.6.32-15-generic"

To obtain the existing menuentry choice number (starting from 0) or the menuentry "string", run "grep menuentry /boot/grub/grub.cfg"

grub-reboot. This command sets the default boot entry for the next boot only. The format of the command is the same as for "grub-set-default" (see above).

For an example of how to enable the "saved" option with a custom menu, see the "Custom User Entries" section.

GRUB_DEFAULT="xxxx" - An exact menu entry, including the quotation symbols, may also be used. In this case, location in the menu will not matter. Example: GRUB_DEFAULT="Ubuntu, Linux 2.6.31-9-generic"

GRUB_SAVEDEFAULT=true* If set to true this setting will automatically set the last selected OS from the menu as the default OS on the next boot. No commands need be run to set the default OS. For this entry to work, the GRUB_DEFAULT entry should be set to saved.

GRUB_TIMEOUT=10 - No change from Grub Legacy. This is the number of seconds before the default entry is automatically booted.

Setting this value to -1 will cause the menu to display until the user makes a selection.

To display the menu on each boot use a value of 1 or higher.

This command defers to the GRUB_HIDDEN_TIMEOUT command. If the GRUB_HIDDEN_TIMEOUT option is interrupted by pressing the SHIFT key, the GRUB_TIMEOUT counter begins its countdown.

Caution: Holding down the "SHIFT" key will not display the menu if "GRUB_TIMEOUT=" is set to "0" .

In addition to editing the file as root, you can also run the following commands the check and change the default timeout value. The first checks the existing timeout, the second replaces the value. Replace T with the new value.

Wait X seconds for a key to be pressed before displaying the menu. If no key is pressed during that time, boot immediately.

GRUB_HIDDEN_TIMEOUT_QUIET=true

Used with the GRUB_HIDDEN_TIMEOUT setting.

true - No countdown is displayed. The screen will be blank.

false - A counter will display on a blank screen for the duration of the GRUB_HIDDEN_TIMEOUT value.

This feature currently appears to be broken; the timeout counter isn't appearing when set to 'false' or not set.

GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`

Determines the descriptive name in the menu entry. (Ubuntu, Xubuntu, Debian, etc.)

GRUB_CMDLINE_LINUX
If it exists, this line imports any entries to the end of the 'linux' command line (Grub Legacy's "kernel" line) for both normal and recovery modes. This is similar to the "altoptions" line in menu.lst

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"
This line imports any entries to the end of the 'linux' line (Grub Legacy's "kernel" line). The entries are appended to the end of the normal mode only. This is similar to the "defoptions" line in menu.lst. For a black screen with boot processes displayed in text, remove "quiet splash". To see the grub splash image plus a condensed text output, use "splash". This line is where other instructions, such as "acpi=off" are placed.

For the GRUB_CMDLINE_LINUX_DEFAULT and GRUB_CMDLINE, quotation marks are required (single or double) if the entry is more than one alphanumeric entry. For example, quiet splash requires single or double quotes, while an entry such as quiet would not.

#GRUB_TERMINAL=console
Uncomment to disable graphical terminal (grub-pc only). This can be useful if the user plans on spending a lot of time in the GRUB 2 command line mode. Scrolling and screen responsiveness will be greatly speeded up. If enabled, Grub background splash images will not be displayed.

#GRUB_DISABLE_LINUX_UUID=true
Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to LinuxUpdate: A bug requires quotation symbols be added for this option to be enabled. Change true to "true" and uncomment the line to eliminate UUIDs for linux entries.

#GRUB_GFXMODE=640x480
You can add this line and remove the # symbol to make it active. This entry sets the resolution of the graphical menu (the menu text size). It provides resolutions supported by the user's graphics card (e.g. 640x480, 800x600, 1280x1024, etc). The setting applies only to the boot menu text.

From the GRUB 2 menu you can display available resolutions by typing "c" and then at the "grub>" prompt type "vbeinfo"

The duration is based on the tempo. A tempo of 60 gives the duration a value of 1 second, 120 is .5, 240 is .25, 480 is .125, etc. The length of the tone can be changed by modifying either the tempo (all tones) or duration (individual tone).

Online documentation is available by typing "info grub --index-search play" in a terminal.

* Entries which are not found in the default file and must be added by the user.

/etc/grub.d/

The files in this folder are read during execution of "update-grub" or "update-grub" commands. The contents are imported into /boot/grub/grub.cfg

The order of the entries in the grub menu is based on the order of the file names. File named with a starting numeral are run before those beginning with a letter. The order the files are run determines the menu order in grub.cfg.
Custom entries can be added to the "40_custom" file or in a newly created file.

Any file created must be executable in order to be included in the grub.cfg file during the "update-grub" command.

00_header

05_debian_theme: Set background and text colors, themes

10_hurd Locates Hurd kernels

10_linux Locates Linux kernels based on results of the "lsb_release" command.

10_lupin Locates Linux kernels in Wubi installs within Windows, among other things.

20_memtest86+: If the file /boot/memtest86+.bin exists, it is included as a menu item.

30_os-prober: Searches for Linux and OS's on other partitions and includes them in the menu.

40_custom: A template for adding custom menu entries which will be inserted into grub.cfg upon execution of the "update-grub" command. This and any other custom file must be made executable to allow importation into grub.cfg.

Adding Entries to Grub 2
Menu entries can be added to grub.cfg automatically or manually.

Automatically.

When "update-grub" is executed, Grub 2 will search for linux kernels and other Operating Systems. What and where is looks is based on the files contained in /etc/grub.d folder.

10_linux searches for installed linux kernels on the same partition.

30_os-prober searches for other operating systems.

Custom User Entries (/etc/grub.d/40_custom).

Entries to grub.cfg can be manually inserted by creating a file in the /etc/grub.d folder.

The name of the file determines the order in the menu. 30_os-prober entries will be placed before 40_custom entries, which will be placed before 50_my-sample entries.

Any created file must be made executable. This can be done as root by running "sudo chmod +x /etc/grub.d/filename".

The files in the /etc/grub.d folder will be read and the contents included in grub.cfg when the "update-grub" command is executed as root.

A sample entry. This file creates a menu item for running the SystemRescueCD (previously installed) from a partition created on sda10. Folders and files must have been copied to the correct location in accordance with the SystemRescueCD if you wish to actually use this entry. Note this entry will not work for a SystemRescue ISO. See Section 14 for instructions on how to add an entry to boot ISO images.

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries. Simply type the
# menu entries you want to add after this comment. Be careful not to change
# the 'exec tail' line above.

Note the new partition naming convention. Devices start counting from "0" as done previously. sda is designated as "hd0", sdb is "hd1", etc. However the first partition is now designated as sda1. Counting partitions does not start with "0". sda5 is "5".

If the user wishes to get visual confirmation in the terminal that the 40_custom file contents are being added when "update-grub" is executed, the following line can be added to the /etc/grub.d/40_custom file:

echo "Adding 40_custom menu entries." >&2

Place this line immediately after the first line - "#!/bin/bash" - and before the "exec tail -n +3 $0" line.

Tip: If you want to have your custom entries at the top of the menu (say you want custom titles), create a new file and name it "07_xxxx". Since the files in /etc/grub.d/ are read sequentially, those in "07_custom" will be placed before those of "10_linux". I recommend not naming a custom menu file lower than 06 so that any theme run from 05_debian_theme is allowed to run before any custom menu is created. After creating the file, run sudo update-grub and then check the value of "DEFAULT" in /etc/default/grub. If it doesn't point to the correct menuentry, change the value of DEFAULT to the correct menuentry value.

Omitting memtest86+: To prevent "memtest86+" entries in your Grub 2 menu, remove the "executable" bit from /etc/grub.d/20_memtest86+. You can do this via a file browser by selecting "Properties (right click), Permissions", or via the command line:

Code:

sudo chmod -x /etc/grub.d/20_memtest86+

Omitting Recovery Mode entries:The file /etc/grub.d/10_linux was recently updated to include a check for recovery mode options. Edit /etc/default/grub and add or change this line:

If you have an older version of /etc/grub.d/10_linux and the above does not work after updating grub, you can prevent "Recovery mode" entries in your Grub 2 menu, by editing /etc/grub.d/10_linux. If there are no conditional "if" statements concerning the recovery mode, place a comment symbol (#) in front of the following lines (at approximately line 146) of the old file:

If you wish to retain one "Recovery mode" entry for insurance, you can add an entry to /etc/grub.d/40_custom which will appear at the bottom of your grub menu.

Building a Totally Customized Menu: Ok, admit you are a control freak and you want to see only what you build yourself - customized titles, no "memtest86+" and no extra kernels. Here is how you do it:

Run sudo update-grub to get the current available kernels.

Copy the desired "menuentry" listings from /boot/grub/grub.cfg to /etc/grub.d/40_custom The entry begins with the line starting with "menuentry" and ends with a line containing "}".

Add any other "menuentry" items you wish to see on the boot menu.

Edit the titles of the "menuentry" line if desired (between the quotation symbols). Do not change the lines following the "menuentry" line. Each entry should start with a "menuentry" line and end with a "}" on the last line.

Remove the executable bit from /etc/grub.d/10_linux, /etc/grub.d/20_memtest86+ and /etc/grub.d/30_os-prober
Removing the executable bit from any file in /etc/grub.d will exclude the file from being included in grub updates.

The updated /boot/grub/grub.cfg file should now contain only sections for "00_header", "05_debian_theme" and "40_custom".

The grub.cfg file will not be updated with the addition of a new kernel. To add a new kernel, make "10_linux" executable, run "sudo update-grub" to refresh the available kernels, and repeat these instructions.

Don't forget to run "sudo update-grub" after making any changes to your /etc/grub.d files.

Manual Editing of grub.cfg
Manual editing of /boot/grub/grub.cfg is not normally encouraged, as it can be overwritten by system operations and updates. grub.cfg is created by various Grub2 scripts, and it is usually preferable to edit the content of the scripts so the changes are retained during updates. The files that should be edited are contained in the /etc/grub.d folders and the /etc/default/grub file. Users making changes to grub.cfg should recognize these changes may be overwritten or should disable the ability of the system to update the grub.cfg file.

In order to discourage its editing, grub.cfg is read-only. If you must edit this file:

Code:

gksudo gedit /boot/grub/grub.cfg

Note: This file is returned to 'read-only' status anytime the update-grub command is run.

Removing Entries from Grub 2
Entries should be removed by editing or removing files in the /etc/grub.d folder. The /boot/grub/grub.cfg file is read-only and should not normally require editing.

Automatically.

Too Many Kernels?

If you are not sure of the kernel you are currently using, in a terminal type "uname -r".

Add the repository as per the instructions, or download the file manually and double-click the .deb file to install.

Ubuntu-Tweak will be available under Applications > System Tools.

To clean the kernels:

Select "Package Cleaner" on the left and ""Clean Kernel" from the right panel.

Press the "Unlock" button at the lower right, enter your password.

Select from the displayed list the kernel images and headers you wish to remove. The kernel in use is not listed.

Press the "Cleanup" button at the lower right to remove the selected kernel images and headers.

Too Many Operating Systems?

Other Operating Systems which have been removed from the computer will also be removed from the menu once "update-grub" is run as root.

Menu items are placed on the Grub2 menu by scripts. If you don't want other Operating Systems to be entered in the menu, disable /etc/grub.d/30_osprober

Run this command to stop the script from running: sudo chmod -x /etc/grub.d/30_os-prober

GRUB_DISABLE_OS_PROBER='true' in /etc/default/grub

Memtest86+

Code:

sudo chmod -x /etc/grub.d/20_memtest86+

Run the update-grub command to allow the changes to be incorporated in grub.cfg

User-Created Entries.

To remove a user-created menu entry, remove the applicable file from the /etc/grub.d folder.

If a custom file contains multiple entries, individual items may be removed and others retained.

Once the file has been removed or edited, run "update-grub" to update grub.cfg.

Grub 2 Splash Images & Theming
There are two distinct areas of this section.

Backgrounds & Fonts: In Grub 2, adding a background image and changing font colors is relatively easy and are detailed briefly below. I've included additional information in the Grub 2 Drop-In Backgrounds & Font Selection thread, which was written specifically for Grub 1.99 (Natty and later) but which can be applied in part in earlier versions.

Themes: Although there are no easy-to-use GUI applications to construct great-looking themes, Grub 2 allows the user to create complex menus if the user wishes to construct them manually. Forum member towheedm has written an extremely comprehensive and well-documented guide to creating great-looking themes with Grub 2. His PDF document and sample files walk you through the process of buidling a custom theme. Take a look at his example in the thumbnail at the bottom of this post. Here is the download link for A Beginner's Guide to Theming GRUB2

The grub2's splash images are normally, but not always, controlled by /etc/grub.d/05_debian_theme. There are additional options in Grub 1.99 & later, and 2 variants in Grub 1.98 (see below).

Grub 1.99 (Natty)
In addition to the methods mentioned in the next section, Grub 1.99 allows the user to simply place an image in the Grub folder. This image will be used as the Grub 2 splash image (background). Here are the details on how it works:Grub 2 Drop-In Backgrounds & Font Selection

Grub 1.98 late + Grub 1.99 (Maverick / Natty )
Rather than edit the /etc/grub.d/05_header or /usr/share/desktop-base/grub_background.sh file, the user can now include the background image designation directly into /etc/default/grub. The path assumes the folder is located in the default system partition.

Grub 1.97~beta4
Find the following line and edit the highlighted area, replacing it with the grub splash image you wish to use (and located in /usr/share/images/grub):

for i in {/boot/grub,/usr/share/images/grub}/moreblue-orbit-grub.{png,tga} ; do

Note: There is a period ( . ) following the filename.

At one point Grub 2 splash images were downloaded and stored in /usr/share/images/desktop.base If this is where your grub images are stored, change the address in the previous command accordingly ( ... /usr/share/images/desktop-base} ... ).

Changing Menu Resolutions
If the user wishes to change the resolution of the GRUB 2 screen while using a splash image follow these steps:

Set the desired resolution in /etc/default/grub

Change the value of GRUB_GFXMODE= (Example: GRUB_GFXMODE=800x600)

If unsure of what resolutions are available to GRUB 2 they can be displayed by typing vbeinfo in the GRUB 2 command line. The command line is accessed by typing "c" when the main GRUB 2 menu screen is displayed.

Select an image of the same size and make the change in /etc/grub.d/05_debian_theme

The image name is located in the line beginning with "WALLPAPER=" (Grub 1.98) or " for i in {/boot" in Grub 1.97-beta.

If an image of the correct size is not used, the menu may not be positioned correctly.

Use the image editor of your choice to create/resize an image to the correct size.

The user may be able to view the image size via Properties in a file browser (check the Properties Image tab in Nautilus).

Run update-grub as root to add the new settings to /boot/grub/grub.cfg

Basic Password Protection

Note: To reduce the size of this entry, a separate post with information on establishing Grub 2 password protection is located on the Ubuntu forums at: Grub 2 Password Protection and in the links at the bottom of this post.

Grub 2 currently supports unencrypted password protection. Encrypted password protection using PBKDF2, as well as password scripting, is currently under development.

If password protection is enabled, the superuser username and password are required to gain access to the Grub 2 command line and menu editing modes.

The username and/or password do not have to be the same as the Ubuntu logon name/password.

This is basic password security. The name/password are unencrypted; anyone having physical access to the machine and more than an elementary knowledge of how Linux works will be able to access the configuration files and bypass this feature.

Grub 2 password protection is still being developed. Encryption is available in experimental versions only. If password protection is used, recheck your scripts for changes whenever a new Grub 2 update is released. In 1.97~beta4, passwords must be assigned to each desired menu item. In Lucid Lynx, expect Grub 1.97 to password protect the entire Grub 2 menu if a superuser is designated.

How to Boot to the Recovery Mode w/o a Menu Option

If you have Grub 2 set to boot without displaying the menu at all, hold the SHIFT key down until the menu displays. (In Grub it was the ESC key.)

Press any key once the menu is displayed to 'freeze' it. Then arrow to the kernel you want to boot.

Press "e"

Scroll to the end of the "linux /boot/vmlinuz...." line. If displayed, remove "quiet" and/or "splash". Add the word "single" to the end of the line.

Press CTRL-X to boot to the Recovery menu.

Uninstalling GRUB 2
The command line produces a cleaner uninstall and reinstallation. While adding and removing the packages can be accomplished with Synaptic, certain steps must be accomplished in a terminal.

Ensure you have an Internet connection and reliable power source. An interruption of either could leave your system in an unbootable condition.

Code:

sudo apt-get purge grub-common grub-pc

The user will be warned the system will be unbootable without installing another bootloader.

Once the packages are removed, many files will still remain in '/boot/grub'

Install GRUB 2

Code:

sudo apt-get install grub-common grub-pc

The user will be asked for any special commands to add to the default "linux" line. If you aren't sure, leave it blank, press the TAB key to highlight "OK" and press ENTER.

Select the appropriate drive on which to install Grub2 (sda, sdb, etc) by highlighting the entry and pressing the space bar. Normally a partition (sda1, etc) should not be selected.

Code:

sudo update-grub

Reboot

Reinstalling GRUB 2 from LiveCD
If you cannot boot from GRUB 2 and need to reinstall it, here is the simple method. For more details or for advanced options, refer to the Ubuntu community documentation here: Grub2 - Reinstalling GRUB 2:

Boot the Ubuntu Live CD (Try without installing).

From the Desktop, open a terminal - Applications, Accessories, Terminal.

If you aren't sure, run `df -Th`. Look for the correct disk size and ext3 or ext4 format.

Mount your normal system partition:

Code:

sudo mount /dev/sdXY /mnt

If you aren't sure if you mounted the correct partition, once it's mounted run "nautilus /mnt" to inspect the partition. If it is the correct partition, you should see the normal Ubuntu folders such as /bin, /boot, /etc, /home, etc

Example: sudo mount /dev/sda1 /mnt

Note: The partition to mount is normally the partition on which Ubuntu was installed: sda1, sdb5, etc. If you have a separate /boot partition, use the device on which the /boot partition is located. Grub 2 works best when installed in the MBR of the drive to which BIOS boots. Also remember that you mount the partition (including the number) in this step, but you do not include the partition number when you run the "sudo grub-install" command later.

Note: GRUB 2 counts the first drive (X) as "0", but the first partition (Y) as "1"

Only if you have a separate boot partition:

Code:

sudo mount /dev/sdXY /mnt/boot

with sdXY being your /boot partition designation.

Reinstall GRUB 2:

Code:

sudo grub-install --root-directory=/mnt /dev/sdX

Do NOT include the partition number.

Example: sudo grub-install --root-directory=/mnt /dev/sda

Note: Substitute the device on which Ubuntu was installed - sda, sdb, etc. Do not specify a partition number.

See the following thread in the Tutorials section for information and instructions on how to boot Ubuntu and other system ISOs:ISO Booting with Grub 2

Booting from the Rescue Mode
One of the improvements of Grub 2 is the ability to recover from a failed boot from the Grub 2 "grub rescue>" or "grub>" prompt. For a detailed discussion and instructions on booting from the Grub 2 prompt, please refer to this tutorial:HOWTO: Boot & Install Ubuntu from the Grub Rescue Prompt

Restoring GRUB2 / XP / Vista / Win 7 Bootloaderstalsemgeest has written an excellent guide on how to restore the bootloaders of various operating systems following the installation of another one. Make sure you reference the section for "9.10 and Beyond", which is for GRUB 2.

Restoring Windows MBR without a Windows CD
If you want to boot directly to Windows but Grub has overwritten the MBR, the normal procdeure is to use the Windows CD to restore things. If you do not have access to the Windows CD, the following commands will rewrite the MBR, removing Grub and allowing the system to boot directly into Windows.

Boot the Ubuntu LiveCD, open a terminal (Applications, Accessories, Terminal) and enter the following commands. Make sure you correctly identify the Windows device (normally sda):

Code:

sudo apt-get install lilo
sudo lilo -M /dev/sda mbr

Bonus Section: BSD Menuentry - If you need to have an entry to boot into BSD/Windows from the Grub2 menu, here is the menuentry to put into a custom file:

menuentry "FreeBSD" {
insmod ufs2
set root=(hd1,1)
chainloader +1
}

Grub Rescue Image
A bootable Grub 2 rescue image is available for both floppies and CDs. To obtain the images, install "grub-rescue-pc". Once installed, three images are available in /usr/lib/grub-mkrescue. Use the I]grub-mkrescue [/I] command to create the rescue ISO. See the MAN page for more information. Note: A customized rescue ISO only uses the current systems Grub 2 /boot/grub files. No information from /etc/grub.d or /etc/default/grub is imported.

The ISO only boots to the grub prompt. It uses the Grub 2 files found on the ISO; if the problem is with the system's Grub 2 files the rescue ISO should boot. However, the ISO contains no kernels and must be told where to find the correct kernel and initrd files on the system. The user must know the drive/partition on which the boot files are located and the non-Grub files must exist and be uncorrupted.

If the user hasn't made a rescue floppy/ISO, other alternatives include the Ubuntu Installation/LiveCD or SuperGrub Disk.

You must type the entire path and kernel and initrd names if (hdX,Y)/vmlinuz and (hdX,Y)/initrd.img do not exist. You can check by running this command:

ls (hdX,Y)/

If vmlinuz and initrd.img do not exist at (hdX,Y)/, you can simplify the typing using the TAB complete feature.

On the linux line, type "vml" and then TAB to help complete the kernel number. Ensure the complete kernel name is entered. Be sure to fill the kernel number completely, and don't forget the "root=" and "ro" sections of the linux line.

On the initrd line, type "ini" and TAB to fill in a large part of the name. Continue typing/TABBING to ensure the complete .img name is used.

Sections in bold should be changed to match the user's system.

Code:

set root=(hd0,1)
linux (hdX,Y)/vmlinuz root=/dev/sdXY ro
# or if (hdX,Y)/vmlinuz does not exist:
linux (hdX,Y)/boot/vmlinuz-2.6.32.25-generic root=/dev/sdXY ro
# then
initrd (hdX,Y)/boot/initrd.img
# or if (hdX,Y)/initrd.img does not exist:
initrd (hdX,Y)/boot/initrd.img-2.6.33-25-generic
boot

Grub 2 Fallback
There is a little-documented 'fallback' capability which allows Grub 2 to select an alternate menuentry should the default entry fail. Since Grub 2/Natty uses submenus which may alter the way to use fallback, this section covers Grub 1.98/Maverick & earlier.

To designate a fallback menuentry, add the following to /etc/grub.d/40_custom. X is the menuentry number (start counting the grub.cfg menuentries at 0):

set fallback=X

Notes regarding the Grub 2 Fallback Option:

In Maverick, using the title rather than the menuentry number does not appear to work in /etc/grub.d/40_custom

The title can be used if set fallback="<title>" is placed in /boot/grub/grub.cfg, but is not recommended as it will be removed during updates.

Instructions for using the fallback option in Natty/Grub 1.99 will be added once Natty is officially released.

Selected Problems & Bugs

"out of disk" ,"device not found", "no such device" , "root device" Errors
Causes are many, but can be caused by Grub2 not finding partitions/files it is looking for. Some possible areas to explore while troubleshooting:

Does your BIOS see the files? Older BIOS may not see past 8GB or 137GB of the partition. You may need to create a separate /boot partition or adjust the BIOS to use the 'large disk' mode or update the BIOS to allow it to use today's larger disks.

Some users may need to add "rootdelay=90" to the end of the "linux" line in /etc/default/grub. The might be necessary if the system takes a long time to recognize the drive.

The BIOS controller mode may need to be changed. Change the BIOS entry for the SATA Controller from from AHCI to Compatibility mode.

Lubuntu Dual Booters - No Windows Menu
Lubuntu apparently doesn't ship with the package os-prober so Windows will not be added to the Grub 2 menu. To add Windows, install os-prober, update grub and then check to see if Windows is now in the menu:

Grub Update results in "No Such Disk":
A late July 2010 Grub 2 update is causing a "no such disk" error for some users of WUBI, resulting in an unbootable system. If the system doesn't display the original Windows menu, the most likely cause of the failure is that Grub 2 was installed in the MBR and/or on the Windows partition. To correct this, restore the Windows bootloader using this link:How to restore the Ubuntu/XP/Vista/7 bootloader

Whether the failure is due to improper user selections or Grub 2's failure to recognize a Wubi install, it has been reported in the following bug and users can review it for status updates and recovery options when they become available:https://bugs.launchpad.net/wubi/+bug/610898

"Fix Symbol 'grub-puts' Not Found" Error Message: http://www.webupd8.org/2010/05/fix-symbol-grubputs-not-found-when.html
If you can get to a normal installation, run the grub-install command or use the "dpkg-reconfigure grub-pc" command to put Grub onto your current partition. If you have to use the Live CD, use chroot to run these commands (see chroot link in my signature line.

Note: Most of this information has been incorporated, with a few graphics, into a page in the Ubuntu Help site. I will try to keep this post up-to-date and users are free to continue to post comments here. The help page is located here: https://help.ubuntu.com/community/Grub2

meierfra has been busily building pages which detail how to solve many of the common problems users are experiencing with Grub 2. His SourceForge web page should be one of the first stops for those seeking answers to Grub 2 issues.

Lose Ubuntu/Windows After Installing the Other
If you have lost the ability to boot into Windows or Ubuntu following the installation/reinstallation of the other OS it could be an overwritten MBR issue. If the OS was previously working, there is an excellent guide written by talsemgeest that may very well restore the lost OS. Here is the link:How to restore the Ubuntu/XP/Vista/7 bootloader (Updated for Ubuntu 9.10)

No Menu On Initial Boot
If you are already on the Ubuntu Desktop, run "sudo update-grub". This may detect additional operating systems, which may allow the Grub menu to be displayed on the next boot. Otherwise:
Open /etc/default/grub:

Code:

gksu gedit /etc/default/grub

Disable the "GRUB_HIDDEN_TIMEOUT=" line by placing a # symbol at the beginning of the line.
Set "GRUB_TIMEOUT=" to a positive integer (number of seconds to display the menu before automatic selection) or "-1" to wait for the user to press ENTER (no timeout). The entry will look like this:

HP Machines Fails to Load Grub after Using Windows - Bug bug/441941
After installing Grub 2 on a HP machine, the system boots normally until the first time it's booted into Windows. On the next boot, the system hangs at "Grub loading".

Workaround: HP protection tools are rewriting to the MBR when Windows is run. The protecttools app must be removed/disabled. Refer to post #10 in the Bug Report.

"Grub loading. The symbol ' ' not found. Aborted." on Dell machines..
On Dell computers with Dell DataSafe Local Backup (DDSLB) installed, the above message is displayed with a series of characters within the ' ' section. This is a reported bug, bug #482757. Thanks to merry_meercat's post which details how to fix the problem.

"error: unknown filesystem" on old motherboard & BIOS.
If you are using an older motherboard/BIOS, make sure the BIOS and system can read your hard drive. There is a 137GB limit in old BIOS settings that prevents the system from recognizing data placed 'deeper' into the partition. Try creating a /boot partition smaller than 130GB and see if the system now recognizes it. You can also check to see if there is a BIOS update which may eliminate this problem.

Grub "error: out of disk" or "failed to boot default entries".
This error message is sometimes generated when Grub 2 cannot properly write to the file /boot/grub/grubenv. Refer to meierfra'sBoot_Problems:Write page.

"Grub loading. The symbol ' ' not found. Aborted." on Dell machines..
On Dell computers with Dell DataSafe Local Backup (DDSLB) installed, the above message is displayed with a series of characters within the ' ' section. This is a reported bug, bug #482757. Thanks to merry_meercat's post which details how to fix the problem.

Re: Grub 2 Basics

I don't know why grub2 isn't picking it up. I have had a few instances of grub2 not picking up all the kernels scattered over my drives but I don't remember grub2 actually ignoring ones that it located.

Here are a couple of things I do when troubleshooting:

a. Change one of the titles so I know the grub.cfg I see when it boots is the one I am looking at in the editor (i.e. if there are multiple grub.cfg files on your system). You will have to chmod +w to actually edit grub.cfg

b. Search your system for multiple instances of the file.

c. Place the kernel you want to show up in /etc/grub.d/40_custom so at least it shows up when you update grub. At best you will have two instances - the detected and the custom entries; at worst you will have at least the one from the 40_custom file. Don't forget to make the file executable.

Edit: foxy123 has a separate boot partition for his Karmic install as well, so his sda7 entry was correct. The following was written before I found out the separate test-boot partition was linked to the Karmic installation.

I believe the problem is with your partition numbers. First, a disclaimer. I'm relying on the comments in fstab being accurate. Since they aren't updated, they really can't be relied upon unless confirmed via "mount", "sudo blkid", or some other command. So I'm relying on sda6 being the correct partition number. I'm also making the assumption that the Karmic install is on sda6 and not sda7, since it is the sda6 UUID in the boot menu.

Grub 2 counts partitions a bit differently. sdXY, with X being the device (a,b,c) and Y being the partition number (1,2,3). The device starts counting at 0 - sda is device 0. The partitions (and this is a change) start counting at 1, so partition 1 is counted as 1. So sdb3 is device 1, partition 3.

In your setup, sda6 should be listed as (0,6). Try this as your Karmic entry and see if it works correctly. If it doesn't, confirm the device and UUID designations by running "sudo blkid -c /dev/null".